1,722,345 research outputs found
Repetitive process based higher-order iterative learning control law design
No full textIterative learning control has been developed for processes or systems that complete the same finite duration task over and over again. The mode of operation is that after each execution is complete the system resets to the starting location, the next execution is completed and so on. Each execution is known as a trial and its duration is termed the trial length. Once each trial is complete the information generated is available for use in computing the control input for next trial.This thesis uses the repetitive process setting to develop new results on the design of higher-order ILC control laws. The basic idea of higher-order ILC is to use information from a finite number of previous trials, as opposed to just the previous trial, to update the control input to be applied on next trial, with the basic objective of improving the error convergence performance. The first set of new results in this thesis develops theory that shows how this improvement can be achieved together with a measure of the improvement available over a non-higher order law.The repetitive process setting for analysis is known to require attenuation of the frequency content of the previous trial error from trial-to-trial over the complete spectrum. However, in many cases performance specifications will only be required over finite frequency ranges. Hence the possibility that the performance specifications could be too stringent. The second set of new results in this thesis develop design algorithms that allow different frequency specifications over finite frequency ranges.As in other areas, model uncertainties arise in applications. This motivates the development of a robust control theory and associated design algorithms. These constitute the third set of new results. Unlike alternatives, the repetitive process setting avoids the appearance of product terms between matrices of the nominal system dynamics statespace model and those used to describe the uncertainty set. Finally, detailed simulation results support the new designs, based on one axis of a gantry robot executing a pick and place operation to which iterative learning control is especially suited
Impact damage of composite laminates with high-speed waterjet
No full textRain erosion may cause substantial damage to aircrafts during supersonic flight. Such event is investigated here via high-speed waterjet impact on composite laminates. An experimental setup is developed to produce waterjets with the speed up to 700m/s and a finite element model of the waterjet-composite impact event is established. The consistency of experiment and simulation results validates the adopted numerical methods. The distribution of the water-hammer pressure is non-uniform and the maximum pressure occurs near the contact periphery when the water is about to eject laterally. After a high-speed (300∼560m/s) waterjet impacts a composite laminate, the impacted surface depression is observed, and the typical surface damage presents a central region with no visible surface damage surrounded by a faded “failure ring” with resin removal, matrix cracking and minor fiber fracture. Delamination occurs at the interfaces of adjacent layers with unequal dimensions and longitudinal matrix cracking appears on the back surface. Both the velocity and the diameter of waterjets are crucial factors on CFRP damage extents. Water-hammer pressure, the stagnation pressure and propagation of stress waves are failure mechanisms for most matrix damage in CFRP impacted by waterjets.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Higher-order iterative learning control law design using linear repetitive process theory: convergence and robustness
No full textIterative learning control has been developed for processes or systems that complete the same finite duration task over and over again. The mode of operation is that after each execution is complete the system resets to the starting location, the next execution is completed and so on. Each execution is known as a trial and its duration is termed the trial length. Once each trial is complete the information generated is available for use in computing the control input for the next trial. This paper uses the repetitive process setting to develop new results on the design of higher-order ILC control laws for discrete dynamics. The new results include conditions that guarantee error convergence and design in the presence of model uncertainty
Reinforement of Carbon Nanofibers for IPMC Actuators Employing Sulfonated Poly(styrene-b-ethylene-co-butylene-b-styrene) Ionomers Poly(styrene-b-ethylene-co-butylene-b-styrene) Ionomers
No full textSulfonated Poly(styrene-b-ethylene-co-butylene-b-styrene) and Fullerene Composites for Ionic Polymer Actuators
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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